1. Field of the Invention
The present invention relates to a vehicle differential gear having a mechanism to lock a differential operation (differential lock).
2. Description of Background Art
A differential gear is a device to absorb a difference in the number of revolutions between left and right driving wheels upon turning of a vehicle to allocate driving torque to the respective driving wheels while generating a number of revolutions corresponding to the respective vehicle wheels.
Some differential gears have a mechanism to lock a differential operation (differential lock). The differential lock temporarily stops a differential operation of the differential gear to uniformly transmit driving torque to left and right wheels unconditionally. The differential lock typically functions when one of the left and right wheels slips on a road with a small friction coefficient such as a sloppy road and the vehicle cannot escape. In a four-wheel vehicle, a vehicle operating on uneven land and the like, the differential lock is often adopted as a differential gear with a limited-slip differential mechanism. For example, JP-A No. 2008-267561 discloses a differential gear having a limited slip differential mechanism and a differential lock.
In a differential gear with a differential lock as disclosed in the JP-A No. 2008-267561, when the vehicle enters a differential lock status during high speed operation, as a heavy load is applied on the lock mechanism, it is necessary to fortify the lock mechanism. This enlarges the entire device and increases the weight.